PHYSICAL CHANGES DURING COFFEE ROASTING IN ROTARY CONDUCTION-TYPE HEATING UNITS

Coffee beans were roasted in a rotary conduction‐type‐heating unit under constant heating surface or product temperatures ranging from 200 to 240C or 170 to 210C, respectively. the roasting duration was varied from 0 to 70 min through intermittent sampling of coffee beans at selected intervals. There were marked changes in physical conditions of coffee beans during roasting. the specific gravity, bulk density, susceptibility to breakage, and color lightness index L changed from 1.2 to 0.5, 0.7 to 0.3 g/cm³, 20 to 100, and 50 to 12, respectively.     

烤制温度和时间对烧烤草鱼块品质的影响

本实验以草鱼为研究对象,将鲜活草鱼去鳞、头、尾、内脏,切成鱼块,经脱腥、腌制后置于电烤箱中,分别在不同温度(180、200、220 ℃)下烤制15 min以及在相同温度(200 ℃)下烤制不同时间(10、15、20 min),测定烧烤草鱼块的剪切力、色度、水分、灰分和脂肪质量分数及硫代巴比妥酸反应物值、酸价、挥发性成分相对含量,同时分析鱼肉肌原纤维蛋白的理化性质(二级结构、表面疏水性、总巯基和二硫键含量),结合感官评价,探讨烤制温度和时间对烧烤草鱼块品质的影响。结果显示,随着烤制温度的升高或烤制时间的延长,剪切力逐渐增加,L*值呈现下降的趋势,a*值和b*值总体均呈现上升的趋势,烧烤草鱼块的色泽不断加深,烧烤草鱼块的嫩度、色度均呈现先改善后劣变的趋势,感官评分先增加后下降;水分质量分数显著下降(P<0.05),脂肪和灰分质量分数均呈现先降低后增加的趋势,脂质氧化程度总体逐渐加剧,挥发性成分中的醛类物质及醇类物质的相对含量总体呈下降趋势;肌原纤维蛋白的二级结构由稳定状态逐渐向不稳定状态转变,表面疏水性指数(H₀)和二硫键含量逐渐增加,总巯基含量逐渐下降。在20...     

Optimization of roasting conditions according to antioxidant activity and sensory quality of coffee brews

Response surface methodology (RSM) was used to determine the optimal roasting temperature and roasting time of coffee beans used for preparing brews with high antioxidant activity and sensory quality. Green coffee beans (Coffea arabica L. cv. Colombia Organic Tamata) were roasted at temperatures ranging from 140 to 220°C for 2–10 min and were then brewed with dripping hot water. The effects of the roasting conditions on the browning index, antioxidant activity, color, aroma, taste, and overall acceptability of the coffee brewed from the bean were investigated using a second-order central composite design. The quality indicators except the taste were significantly affected by roasting temperature and time, tending to increase and then decrease with increasing roasting temperature and time. Superimposed contour plots indicated that the optimal roasting temperature was 182°C and optimal roasting time was 7 min.     

Changes in color parameters of corn kernels during roasting

Changes in color parameters (L*, a*, b*, ΔE*, h°, and C* values) of corn during roasting were investigated and subsequently described using mathematical models. Corn kernels were roasted for 50 min at 160, 180, 200, 220, and 240°C. The L*, b*, h°, and C* values tended to decrease more rapidly as the roasting temperature and time increased up to 220°C and 50 min, whereas a* and ΔE* values tended to increase. Variation of L* and ΔE* values was found to be proportional to the roasting temperature and time. Variation of L* value during roasting above 180°C was adequately described by a first-order model. Cubic model satisfactorily described changes in all of color parameters over the temperature range. Activation energies of L* and ΔE* values were determined as 34.04 and 79.16 kJ/mol, respectively. Results suggest that L* and ΔE* values may be used as color control indicators during roasting of corn kernels.     

Optimization of the roasting temperature and time for preparation of coffee-like maize beverage using the response surface methodology

The response surface methodology (RSM) was used to determine the optimal roasting temperature and time for preparing a coffee-like beverage from maize kernels. Maize kernels were roasted at different temperatures (160–240 °C) for different lengths of time (10–50 min) and subsequently extracted with hot water. Yield, levels of free sugar and phenolic compounds, antioxidant activity, and sensory scores for overall preference of the maize beverage were significantly affected by the roasting conditions. Roasting temperature was the most important factor affecting the quality indicators of the maize beverage. Surface and contour plots indicated that the optimal roasting temperature and time were 207 °C and 24 min, respectively.     

The thermal kinetics of texture change and the analysis of texture variability for raw and roasted hazelnuts

Texture changes of hazelnuts which were dry roasted at temperatures from 120 to 180 °C, for durations ranging from 5 up to 60 min, were studied using instrumental analysis. The textural changes in hazelnuts were represented by the fracture force obtained from compression tests. The magnitudes of the parameters for the corresponding texture change model were determined using one step non‐linear regression. The order of the reaction was found by plotting isothermal curves of texture response against time; statistical analysis of the data showed that it was best represented by a first‐order reaction. The rate constants were assumed to have an Arrhenius‐type dependence on temperature. The activation energy and the frequency (pre‐exponential) factor at a reference temperature (150 °C) were determined to be 39.25 kJ mol^?1 and 0.0421 s^?1, respectively. Young's modulus and the fracture stress for roasted hazelnuts were calculated to be 4.93 and 1.54 MPa, respectively. Both roasting temperature and time had significant effects on the textural changes in hazelnuts, and the variability in the texture decreased during the roasting process. The physical properties of hazelnuts were correlated with the texture response. A possible major factor causing the high variability in texture was the internal cavity present at the core of each hazelnut. The development of a model of the thermal kinetics of texture change over a large roasting temperature and time range should allow optimization studies to be used for determining the best roasting schedule in terms of delivering the required product texture.     

Influences of superheated steaming and roasting on the quality and antioxidant activity of cooked sweet potatoes

Roasted sweet potato is a popular food because of the attractive aroma produced by the Maillard reaction. However, the roasting process may lead to charred skin. Cooking with superheated (saturated) steam provides a solution to this problem. As the results show, when comparing sweet potatoes cooked by superheated steam, and those roasted for 40 min, respectively, the degree of gelatinisation could reach as high as 95% with only 140 °C superheated steam, while roasting required temperatures up to 240 °C. Moreover, in appearance, the skins of the sweet potatoes cooked using superheated steam were not charred like the roasted ones. However, sweet potatoes roasted at 240 °C for 60 min had the highest overall sensory score. When comparing the antioxidant activity, the sweet potatoes cooked by superheated steam had the highest content of total phenol and flavonoids, the best scavenging ability of 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and the highest ferric‐reducing ability of plasma (FRAP).     

Color and Volatile Analysis of Peanuts Roasted Using Oven and Microwave Technologies

Roasted peanut color and volatiles were evaluated for different time and temperature combinations of roasting. Raw peanuts were oven roasted at 135 to 204 °C, microwave roasted for 1 to 3 min, or combination roasted by microwave and oven roasting for various times and temperatures. Volatiles were measured using selected ion flow tube mass spectrometry. L* values were used to categorize peanuts as under‐roasted, ideally roasted, and over‐roasted. The total roasting time in order to achieve ideal color was not shortened by most of the combination treatments compared to their oven roasted equivalents. Oven before microwave roasting compared to the reverse was found to significantly increase the L* value. Peanuts with the same color had different volatile levels. Hexanal concentrations decreased then increased with roasting. Pyrazine levels increased as roasting time increased, although oven at 177 °C treatments had the highest and microwave treatments had the lowest levels. Volatile levels generally increased as roasting time or temperature increased. Oven 177 °C for 15 min generally had the highest level of volatiles among the roasting treatments tested. Soft independent modeling of class analogies based on volatile levels showed that raw peanuts were the most different, commercial samples were the most similar to each other, and oven, microwave, and combination roasting were all similar in volatile profile.     

Volatile profile of cashews (Anacardium occidentale L.) from different geographical origins during roasting

Abstract: Volatile compounds were quantified in the headspace of Indian, Vietnamese, and Brazilian cashews, both raw and during roasting by selected ion flow tube‐mass spectrometry. The optimum roasting times based on color measurements were also determined. Raw cashews were oil roasted for 3 to 9 min at 143 °C and color and volatiles measured. An excellent correlation, following a pseudo 1st‐order reaction, was found between L* value and roasting time; darkness increases as roasting time increases. The optimum roasting time was 6, 8, and 9 min for Vietnamese, Indian, and Brazilian cashews, respectively. Raw cashews had lower concentrations of volatiles than roasted cashews. Most volatiles significantly increased in concentration during roasting of Brazilian, Indian, and Vietnamese cashews. Only a few volatiles significantly decreased during roasting. Ethanol and 1‐heptene significantly decreased during roasting in Brazilian cashews and toluene decreased in Vietnamese cashews. Brazilian cashews had significantly higher levels of most volatiles than Indian and Vietnamese cashews. Most volatile levels in Indian and Vietnamese cashews were not significantly different. Of the volatiles, Strecker aldehydes, including methylbutanal, 2‐methylpropanal, and acetaldehyde, were at the highest concentration in roasted cashews. The Maillard reaction contributed to the formation of most of the volatiles in cashews from the 3 countries. There was also degradation of sugars to form furan‐type compounds and oxidation of lipids to form alkanals such as hexanal. Practical Application: The volatile profile during roasting of cashews can be used to determine the best roasting time for each type of cashew. The rate of color development and the production of volatiles differ for the cashews from the 3 geographical locations.     

Infrared heating for dry-roasting and pasteurization of almonds

The use of infrared (IR) heating for improving the microbial safety and processing efficiency of dry-roasted almonds was investigated. Almonds were roasted at 130, 140 and 150 °C with three different methods: IR roasting, sequential infrared and hot air (SIRHA) roasting, and traditional hot air (HA) roasting. The heating rate and pasteurization efficacy of almonds under different roasting methods and temperatures were evaluated. Pediococcus sp. NRRL B-2354 was used as a surrogate for Salmonella enterica Enteriditis PT 30 for evaluating the pasteurization efficacy of different processing methods and conditions. When SIRHA roasting at 130, 140 and 150 °C roasting temperatures was used to produce medium roasted almonds, 4.10-, 5.82- and 6.96-log, bacterial reductions were achieved with 38%, 39% and 62% time saving compared to HA roasting at each temperatures, respectively. The decimal reduction time of the bacteria at all roasting temperatures were calculated for SIRHA roasting as 8.68, 3.72 and 1.42 min, respectively, with a correlation coefficient greater than 0.92 and the thermal resistance constant was found as 25.4 °C. The total color change followed zero-order reaction kinetics and the activation energies were 73.58, 52.15 and 67.60 kJ/mol for HA, IR and SIRHA roasting, respectively. No significant difference (p > 0.05) was observed in sensory quality of medium roasted almonds processed with different roasting methods. We conclude that the SIRHA roasting is a promising new method for the production of dry-roasted pasteurized almonds.     

Effect of added phosphate and type of cooking method on physico-chemical and sensory features of cooked lamb loins

This study evaluated the effect of brining with phosphates on the physico-chemical and sensory features of sous-vide and roasted cooked lamb. Lamb loins (n = 48) were injected with either 10% w/w of distilled water or a solution containing 0.2% or 0.4% (w/v) of a mixture of phosphate salts. After injection, samples were either sous-vide cooked (12 h—60 °C) or oven roasted (180 °C until 73 °C of core temp.). Expressible moisture, cooking loss, instrumental color, pH, water holding capacity, instrumental texture and sensory properties were evaluated. Brining with phosphates led to lower cooking loss in both sous-vide and oven roasted samples, but only the former showed significantly higher moisture content. Phosphates increased instrumental hardness and shear force values in sous-vide samples, while this effect was not as evident in roasted ones. Toughness was reduced and juiciness was improved as a consequence of phosphate addition. Overall, injection of a phosphate solution appears as a potential procedure for improving sensory textural features of cooked lamb whole cuts.     

米茶的焙炒工艺研究

以碎米为原料,经浸润焙炒等工序制得米茶,研究米茶焙炒工艺对米茶茶汤感官品质的影响。结果表明,米茶茶汤的色彩是在焙炒过程中形成的,茶汤以黄色为主,略带绿色,透明度较高。较长的焙炒时间和较低的加水量有利于增强茶汤黄绿色和色彩纯度,使感官品质增加。米茶茶汤的色泽、滋味、香气与红度呈显著的负相关,与黄度、彩度呈显著的正相关。适宜的工艺为,按碎米质量的5%加水浸润5 min,于150℃下焙炒40 min,用该工艺制作的米茶的汤汁清亮,具有浓郁的稻米焦香风味。     

Determination of optimum processing conditions for hot‐air roasting of hulled sesame seeds using response surface methodology

Sesame paste (tahin) is produced by milling hulled, roasted, sesame seeds. In this study, a hot‐air roasting process for the production of sesame paste was optimised by response surface methodology (RSM) over a range of air temperatures (120–180 °C) for various times (30–60 min). The colour parameters (L, a and b values), browning index (BI), hardness, fracturability and moisture content of the seeds were used as response parameters to develop predictive models and optimise the roasting process. Increases in roasting temperature and time caused increases in the a and b values and in the BI. The hardness and fracturability of seeds also decreased with increasing roasting temperature and time. The quadratic and linear models developed by RSM adequately described the changes in the colour values and textural parameters, respectively. The result of RSM analysis showed that all colour parameters and textural parameters should be used to monitor the roasting of sesame seeds in a hot‐air roaster. To obtain the desired colour and texture, the optimum roasting range for production of sesame paste was determined as 155–170 °C for 40–60 min. Copyright © 2006 Society of Chemical Industry     

Kinetics of ascorbic acid degradation and colour change in ground cashew apples treated at high temperatures (100–180 °C)

Ascorbic acid (AA) degradation and colour changes, measured by the lightness index (L*), were determined in cashew apples (at low dissolved O₂ concentrations) heated at high temperature (100–180 °C) in a hermetically sealed cell. A nonisothermal method was developed to estimate thermal degradation kinetics. The results showed that reaction kinetics during heat treatments were well represented by first‐order reactions. The temperature dependence of the kinetic constants was described by an Arrhenius type equation. The activation energy (E_a) for AA degradation and lightness index were 94 ± 3 and 98 ± 3 kJ mol^?1, respectively. The reaction rate constant at 140 °C for AA degradation (64 × 10^?5 ± 3 × 10^?5 s^?1) was twice that for the lightness index change (33 × 10^?5 ± 2 × 10^?5 s^?1). Results allow generating temperature profiles of heat processes that would help preserve the AA of cashew apples as well as control the colour formation during high‐temperature processes.     

Roasting influences on molecular species of triacylglycerols in sesame seeds (Sesamum indicum)

Sesame seeds were roasted at different temperatures (180–220 °C) using a domestic electric oven. Molecular species and fatty acid distributions of triacylglycerols (TAGs) isolated from total lipids in the sesame seeds were analysed by a combination of argentation thin‐layer chromatography (TLC) and gas–liquid chromatography. A modified argentation TLC procedure, developed to optimise the separation of the complex mixture of total TAGs, provided 11 different groups of TAGs, based on both the degree of unsaturation and the total length of fatty acid groups. Fatty acid methyl ester analysis was performed to determine the composition of each zone. Eleven molecular species of TAGs were still detected in the sesame seeds following roasting treatment. Dilinoleolein (33.7–35.8%), palmitoleolinolein (20.3–22.8%), dioleolinolein (15.0–15.4%) and trilinolein (8.8–10.7%) were the main components during roasting. However, roasting for 10 min at 220 °C caused a significant decrease (P < 0.05) not only in molecular species containing more than four double bonds, but also in the amount of diene and triene species present in TAGs (with a few exceptions). These results suggest that no significant changes in molecular species or fatty acid distribution of TAGs would occur within 25 min of roasting at 180 °C, ensuring that a good‐quality product would be attained. © 2000 Society of Chemical Industry     

Phytochemical profiles of black and yellow soybeans as affected by roasting

The current research aimed to compare the changes of phytochemicals, antioxidants, and anti-nutritional factors of yellow and black soybeans upon roasting. Yellow soybean was roasted at 210°C for 35 min and 230°C for 25 min, and black soybean was roasted at 210°C for 30 min and 230°C for 25 min. Isoflavones were significantly increased after the roasting process, while trypsin inhibitor was significantly decreased. The roasting process combined with the soaking process led to decrease in anthocyanin, soyasaponin, and antioxidant capacities. Black soybeans had more apparent variations in compounds than the yellow soybeans. For black soybeans, the processing under 230°C for 25 min presented more decrease in trypsin inhibitor and anthocyanin content. The roasting at a high temperature and short time produced products with a light color. Roasting combined with the soaking process had negative impacts on both yellow and black soybeans, but there were slight differences in the resultant compounds between different roasting temperatures.     

Effect of roasting conditions on color and volatile profile including HMF level in sweet almonds (Prunus dulcis)

Microwave, oven, and oil roasting of almonds were used to promote almond flavor and color formation. Raw pasteurized almonds were roasted in a microwave for 1 to 3 min, in an oven at 177 °C for 5, 10, 15, and 20 min; and at 135 and 163 °C for 20 min, and in oil at 135, 163, and 177 °C for 5 min and 177 °C for 10 min. Volatile compounds were quantified in the headspace of ground almonds, both raw and roasted, by selected ion flow tube mass spectrometry. Strong correlations were found between L value, chroma, and 5-(hydroxy methyl)-2- furfural; and were independent of roasting method. Raw almonds had lower concentrations of most volatiles than roasted almonds. Conditions that produced color equivalent to commercial samples were 2 min in the microwave, 5 min at 177 °C in the oven, and 5 min at 135 °C in oil. Microwave heating produced higher levels of most volatiles than oven and oil roasting at commercial color. Sensory evaluation indicated that microwave-roasted almonds had the strongest aroma and were the most preferred. Oil-roasted almonds showed significantly lower levels of volatiles than other methods, likely due to loss of these volatiles into the oil. Alcohols such as benzyl alcohols and strecker aldehydes including benzaldehyde and methional were at higher concentrations than other volatiles in roasted almonds. The oxidation of lipids to form alkanals such as nonanal and degradation of sugars to form furan type compounds was also observed. The Maillard reaction contributed to the formation of more of the total volatiles in almonds than the lipid oxidation reaction. PRACTICAL APPLICATION: The level of 5-(hydroxy methyl)-2- furfural (HMF), color, volatile profile, and sensory perception can be used to develop the best roasting method, time, and temperature for almonds. The rate of color development and the production of volatiles differ under different roasting conditions. Based on the color, volatile, and sensory assessments of the 3 almonds, the use of microwave technology as a process for roasting almonds reduces processing time and leads to an almond product with better flavor than oven or oil roasting.     

Effect of processing on the quality of edible argan oil

Sensory quality of edible oil is essential to get the consumer acceptance. Modifications during processing can alter edible oil sensory quality. The storage stability and sensory quality of argan oil prepared from (1) mechanically pressed unroasted kernels, (2) mechanically pressed roasted kernels, (3) hand-pressed roasted kernels, and (4) hand-pressed roasted kernels coming from goat-digested fruits was studied at room temperature and under accelerated conditions (60 °C). The roasting process had a positive effect on storage stability of the resulting oils, while argan oil prepared from mechanically pressed roasted kernels provides the optimum storage stability. Oil from hand-pressed roasted kernels originating from goat-digested fruits was not suitable for human consumption because of the unpleasant taste and odoûr. Only oil from mechanically pressed roasted kernels did not produce negative sensory attributes like fusty or Roquefort cheese.